Rheostat.



4 R. L. WATKINS.

RHEOSTAT. APPLIoATIoN FILED MAY 22, 1911. 1,082,982, Patented Dee. 3o, 1913.

ya NVENTUH www@ M// ATTORNEY E. L. WATKINS.

RHEOYSTAT. v APPLICATION FILED MAY 22, 1911.

Patented Dec. 30, 1913.

2 SHEETS-SHEET 2.

WITNESSES w ATTORNEY nonna/r L. WATKINS, .or NEW YORK, N. Y.

RHEosrA'r.

Specication of Letters Patent.

Patented Dee. 30,1913.

Application led May 22. :1911. Serial No. 628,860.

To all whom 'it may concern: l

Be it known that I, ROBERT L. WATKINs, a citizenlof fthe United States, and a resident of the'` borough of Manhattan, in the city, county, and State of New York, United ,States of America, have invented certain forth in the appended claims.

Referring to the drawings, Figure 1 is a plan view of a `preferred form of my invention, in its folded lcondition,'and Fig. 2 is a plan view of the Same unfolded or open.

Fig. 3 is a side elevat-ion of the folded device withl one of the covers broken away and removed. In Fig. 4 I have shown a detail of construction, this figure being a plan viewof the end of one of the resistance elements or leaves,l as I lshall call them, together with the collar and lugi to which it is aihxed.

Fig. 5 shows the contact pins which are used with this device. Fig. 6 is a side elevation of anotherV form ofthe rheostat which Ihave invented. Figs. 7 and 8 are a rear elevation and a plan view, respectively, of the device shown in Fig. 6. Fig. 9 is a rear elevation of another modified structure embodying my invention. This is shown inside elevation with the top cover removed, in Fig. 10, and in plan view in Fig. 11.

Like characters of reference designate corresponding vparts in all of the figures.

10 designates a resistance element or ,leaf

which com rises a Athin body or sheet 11 ofv some suita le insulating material, prefer- .ably mica. Supported upon opposite sides of thissheet and l ing ila't against the surfaces'thereof are t e convolutions of a continuous resistance wire 12. This may be threaded through holes 13 drilled through heldin place so that adjacent parts of it cannot come in contact with each other, `and so that it may not slip out of place when it is expanded by heat.

Over one edge of each leaf are bent two copper. or other metallic strips 14 and 15 which are separated from each other. The opposite ends of the resistance wires are connected with these strips. To each strip is connected a boss or' collar such' as 20, through the center of which is bored a hole 21.k In Figs. 1 and 2 live of these leaves 10, 10A, 10B, 10C, and 10D are shown, and from these figures it ,maybe seen that they are offset from a line drawn -throu h the center of the hole 21 and parallel lwith the folded leaves, and that'the offset of all of the leaves is different. 22 and 23 designate covers for this device. These covers may be made of plain sheets of mica bound on all four sides by strips of copper 24. Aixed to this binding on the inner edge are collars such as 20, and these covers are also offset vfrom the collars. A pin 25 runs through the holes in all of the collars, and hinges the covers and the resistance leaves together. Surrounding this pin is a sleeve 26 of insulation. The lower end 27 of the in preferably projects below the lower colar so that it may be inserted .in a hole in a table, box, or pedestal to hold the device in an upright position.

In order to more clearly specify the conlars, above the top one, and below the botthe resistance leaves-are in. alinement witheach otherjand the lower lugs are `aleoin alinement with each other in a dierent angular position. Also, these lugs are so placed that when they are thus in alinement the covers and the resistance leaves will be spaced apart equally.

33 is a contact pin of slightly larger diameter than that of the holes 31. A conductor v34 is aflixed to it., This pin is arranged to be thrust down through all of the holes 31 in the lower set of lugs. The fact that these lugs are split allows for this and also insures a good electrical connection between the conductor 34 and the copper strips 15, and one of the ends of each of t-he resistance wires.

35 is another contact pin to which a conductor 36 is attached. This is arranged to be thrust through two or more of the upper lugs, and if desired, a screw 37 may be provided to hold it in place. If this pin is thrust through only twol of the lugs, that is, the cover vlug 2OA and the upper lug20C of the' resistance leaf- 10, this' one resistance leaf will be included inthe circuit between the conductors 34 and 36. By pushing pin 35 down through another lug 20E, another resistance leaf 10A will be included in the circuit in parallel with the resistance leaf 10. Similarly, three, four or all of the resistance leaves may be included in the circuit.

The resistance wires 12 are preferably so proportioned that they havean equal resistance, so that each will permit a passage of the same amount of current; for example, thel resistance wire of each leaf may be of such dimensions as to allow the passage of one ampere on a 110 volt circuit. Then, by adjusting the position of the pin 35, the rheostat may be madeto allow one, two, three, four or five amperes to pass. Of course, more or less than five resistance leaves may be provided.

Among other advantages of this device are that it affords large radiating surfaces spaced apart to give ample ventilation7 and when folded it may be easily carried in the pocket. The resistance leaves are protected by the covers especially when folded.

The device shown in Figs. 6, 7 and 8 embodies some of the novel features of the form vof my invention which has been already described. In these figures the resistance leaves of mica or other suitable sheet-like insulating material are designated by 40, 40A, 40B and 40C. Each of these is provided with rows of small holes 13 through which the continuous resistance wire 12 is threaded. Over one edge of each sheet are folded metallic strips 41, 42, separated from each other, to which the ends of the resistance wire 12 are connected. Over the'other three edges of each leaf is folded a metallic binding 43, similar to the binding 24, which is over the four edges of the covers 22. 23 in the device shown in Figs. 1 and 2.

These bindings stiften the structure and protect it from mechanical injury. Binding screws 44, 45 pass `through holes in the strips 41, 42 and in the mica, and through other metallic blocks 46, preferably rectangular in shape. On the ends of these screws are nuts 47, 48. Thus the leaves are rigidly held in parallelism with air spaces between them. They are also electrically connected as one of the ends of each resistance wire is connected with the screw 44 and the opposite end of each wire is connected with the screw 45. A greater or lesser number of resistance leaves may thus be built up to malte a rheostat of desired resistance and one in which the carrying capacity increases as its resistance decreases.

The other modification which is shown in Figs. 9, 10 and 11 is somewhat similar. But in this case each resistance leaf, such as 50, is constructed of two sheets of mica 51, 52 placed side by side with notches or side openings 13A cut in the longitudinal edges thereof. Over one of the transverse edges of each sheet are bent'metallic lugs such as 53, 54, and between them and separated therefrom is a metallic strip 55 which holds the two sheets of each leaf together. A similar strip 56 is bent over the opposite end of each leaf for the same purpose.

The resistance wire 12A is connected with the lug 53 and is wound around the sheet 51 in the notches 13A therein. Then it is carried down to sheet 52 and is wound around it in its notches back to the lug 54 to which it is connected.

57 and 5S are clamps which hold the leaves together by means of screws in one side thereof. Metallic blocks 59 are interposed between the lugs 53, 54 in line with the clamp screws. These space the leaves apart and connect adjacent ends of the resistance wires together electrically. A supporting bar 60 is connected with each of these clamps 57 and 58 but is insulated therefrom. One end 61 of this bar projects to one side of the device .and may be threaded as shown. Bymeans of this projecting end the device may be supported.

63, 63 are mica covers held over the sides of this device by wires 64.

That I claim is.-

1. A folding rheostat comprising a plurality of resistance leave/s4, a pair of collars for each of the leaves, a [pivot passing through all of the collars, and a pair of contact pins, one of said pins being arranged to be thrust through portions of one of each pair of collarsn and the other pin arranged to be thrust through portions of a desired number of the other ones of said pairs of collars.

2. A folding rheostat comprisingl a plurality of resistance leaves, each leaf having a sheet-like body of insulation and the resistance material wound about said body, a pair of collars for each of the leaves in axial valinement with one another, a pivot passing through all the collars, said leaves being oil"- set from one another by varying amounts;

and a pair of contact pms, one of said pins being arranged to be thrust through portions of one of each pair of collars to hold said leaves apart and the other in arranged to be thrust through portions o? a desired number ofthe other ones of said pairs of collars.

3; A folding rheostat comprising aplurality of resistance leaves, each leaf having a shcet of mica with openings therein, and a resista-nce wire wound about ysaid sheet through the openings, a pair of collars for each ofthe leaves in axial alinement with one another, the ends of each resistance'wire being connected to the collars of its resistance sheet, a pivot passing through all of the collars, mea-ns for Jinsulating the pivot from the collars;,and a pair of contact pins,

, one of said pins being arranged to be thrust through portions vof one of each pair of collars to hold said leaves apart, and the other l pin larranged to bethrust through portions of a desired number of the other ones of said pairs of collars, the pins being arranged to electrically connectthe resistance wires together.

l4. A folding rheostat comprising a plu,

rality of resistance leaves, each leaf having'asheet of mica with openings therein, a yresistance wire vwound about each sheet through said` openings, a pair of covers ofy insulating material; a pair of collars for each of the leaves and the covers in axial alinement with one anothera pivot passing through all of the collars, means for insu# lating said pin from the collars, and means for insulating the collars from one' another, said pivot being elongated to support the rheostat; and a pair of contact pins, one of said pins being arranged v tol be thrust through portions of one of each pair of collars to hold said leaves apa-rt, and the other 6. A folding rheostat comprising a plu? rality of resistance leaves, a pair of collars aiiixed to each of said leaves in axial alinement with one another, a pivot through the collars, lugs projecting from the collars in diferent angular directions, said lugs being arranged to bemoved into two axial lines when the leaves are spread apart, and a pair of contact pins arranged. to be thrust through said lugs.

7 A folding rheostat comprising' a plurality of resistance leaves, resistance wires thereon, 'a pair of collars affixed to each of said leaves in axial alinement with one another, al pivot through the collars, connections between the ends of the resistance wires .and the collars on their respective sheets, lugs projecting from the collars 1n dierent angular directions, said lugs b eing arranged to be moved into two axial lines when the 4leaves are spread apart, and a pair of contact4 pins arranged to be thrust through said lugs to hold the, sheets apart and to connect a desired number of the resistance wires to- ERNEST W. MARSHALL, ELLA 'I poH. 

